To combat the influx of spammers lately, I've now turned on 'new member moderation'.

So any new members now need to be 'approved' before they have permission to post.

Spammers will just be stuck in the queue and not approved, and new legitimate members will be permitted to join.

It might mean a small delay for new members before they're able to post - apologies for any inconvenience, but it's better than continuing with how it is now, and the current effort the moderators have to go to to keep deleting and banning the bots and spammers.

Good call Mike.
Genuinely interested parties aren't going to be fazed by having to wait a day or so.
A message delivery to new members that outline the rules is probably a good idea too (Can thast be automated in the system?), so they know up front what is tolerated, and what is not.

On forum I used to help out on a few years ago, we had a terrible problem with spammers. IIRC there was a vBulletin module that checked blocked IP addresses (reported via spam-o-matic to stopforumspam, plus we checked Spamhaus or similar) and prevented registrations. That got the bots, but there were still some human spammers that got through. Auto moderation was a big help, but even then, a handful of determined spammers waited out the first five moderated posts (as I think it was) to be able to spam. Still, this'll cut it down enormously.